Exhaust treatment device for automotive vehicle having one-piece housing with integral inlet and outlet gas shield diffusers

ABSTRACT

An exhaust treatment device for an internal combustion engine includes a generally cylindrical substrate and sealing system which are swaged in place within a one-piece housing. The one-piece housing includes segmented inlet and outlet gas shields and diffusers which are spun from a single piece of tubing which also contains the substrate. The spun inlet and outlet gas shields and diffusers have segmented configurations including multiple concave and convex sections produced by spin-forming of the housing. The exhaust treatment device is assembled without the need for welding or any other high temperature operation.

This is a division of application Ser. No. 08/984,497, filed Dec. 03,1997, now U.S. Pat. No. 5,980,837, issued Nov. 09, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exhaust treatment device, which may,for example comprise a catalytic device having a one-piece cylindricalhousing, preferably formed of metal, with integral inlet gas shields anddiffusers which may be spin-formed.

2. Disclosure Information

The tailpipe emission control laws applicable to automotive vehicles invarious countries are becoming increasingly stringent. Tighter standardsdemand more precise air/fuel ratio control. This is possible only if airleaks in the exhaust system are kept to an absolute minimum, because airleaks cause a loss of air/fuel ratio control capability. A secondimportant consideration relates to the need to rapidly “light off”exhaust treatment devices. Rapid light off requires that certain exhausttreatment devices be located close to the vehicle's engine. Thus, it ishighly desirable to have an exhaust treatment device which packages inan extremely small volume, and which, therefore, may be mounted inengine compartment or the toeboard area of a vehicle, or in other areaswhich do not offer much space for an exhaust treatment device.

Another objective of automotive manufacturers is to reduce cost ofvehicles; engine exhaust treatment systems comprise an expensive vehiclesystem. The present exhaust treatment device, while allowing much moreflexible packaging, also allows lower cost because welding andadditional parts are eliminated.

U.S. Pat. No. 4,969,264 discloses a catalytic converter and substratesupport having a swaged center section and ram-formed ends.Unfortunately, the design of the '264 patent is not suitable for use asan automotive catalytic converter because the ram-formed ends do notprovide any protection against undercutting of the support system by theexhaust gases. And, ram forming in close proximity to a catalystsubstrate may have the unfortunate consequence of breaking thesubstrate.

The inventors of the present device have determined that a segmentedinlet gas shield and diffuser may be spin-formed rather than ram-formedso as to provide a gas shield, greatly reducing exhaust gas impingementupon the catalytic substrate sealing and support system, while alsoproducing a device of leakproof construction and with a reduced packagevolume. Additionally, an exhaust treatment device, according to thepresent invention, having integral diffusers, may be mated with exhaustpipes without a need for additional extensions.

SUMMARY OF THE INVENTION

An exhaust treatment device for an internal combustion engine includes asubstrate, generally cylindrical in shape and having a cylindrical outersurface extending between an inlet surface and an outlet surface, and asealing system applied to the cylindrical outer surface. A one-piece,generally cylindrical housing containing the substrate and for directingthe flow of exhaust gas to and from the substrate, includes a centerportion swaged upon the substrate such that the sealing system isuniformly compressed and a segmented inlet gas shield and diffuser. Theinlet gas shield and diffuser includes a first concave segment extendingbetween the center portion of the housing and a first convex segmentwhich is tangential to the inlet surface of the substrate such thatimpingement of exhaust gas upon the sealing system is inhibited. The gasshield and diffuser further comprises a second concave segment extendingbetween the first convex segment and a second convex segment having atermination to which an exhaust inlet pipe may be attached. A segmentedoutlet gas shield and diffuser comprises a first concave segmentextending between the center portion of the housing and a first convexsegment which is tangential to the outlet surface of the substrate suchthat impingement of exhaust gas upon the sealing system adjacent theoutlet surface of the substrate is inhibited, with the outlet shield anddiffuser further comprising a second concave segment extending betweenthe first convex segment and a second convex segment having atermination to which an exhaust outlet pipe may be attached.

The first concave segment of the inlet gas shield and diffuser has aradius of curvature which is approximately twice the radius of curvatureof the first convex portion. The first concave segment of the inlet gasshield and diffuser has a radius of curvature with a length which isabout one-tenth of the maximum diameter of the generally cylindricalhousing. Also, the first convex segment of the inlet gas shield anddiffuser has a radius of curvature with a length which is aboutone-fifth of the maximum diameter of the generally cylindrical housing.

According to another aspect of the present invention, a sealing systemcomprises a wire mesh mat extending substantially the entire length ofthe substrate with the mat terminating at both ends with a metallicZ-shaped seal. The inlet gas shield and diffuser and outlet gas shieldand diffuser may be spin-formed after the substrate has been swaged andplaced within the housing. Other alternatives are possible for thespin-forming, regarding the precise sequence of locating a substratewithin the housing prior to spin-forming one end of the housing. Ineither event, the first concave segment of the inlet gas shield anddiffuser extends inwardly at approximately 45° to the cylindrical outersurface of the substrate.

According to yet another aspect of the present invention, a process forassembling an exhaust treatment device comprises the steps of insertingan exhaust treatment substrate into a cylindrical metallic tube,reducing the diameter of the tube by swaging such that the substrate isheld firmly in place within the tubing, and spin-forming gas shieldingdiffusers from the tube at opposite ends of the exhaust treatmentdevice. It is an advantage of the present invention that an exhausttreatment device made according to this invention will be of one-piece,leak-proof construction.

It is a further advantage of the present invention that an exhausttreatment device made according to this invention will be economical toproduce.

It is yet another advantage of the present invention that an exhausttreatment device made according to this invention will have smallpackage volume and therefore will be able to fit into smaller locationsin all types of automotive vehicles.

It is yet another advantage of the present invention that an exhausttreatment device made according to this invention may be produced withflexible manufacturing systems, lending themselves readily to changes inlength and diameter of the exhaust treatment device.

It is yet another advantage of the present invention that an exhausttreatment device made according to this invention may be producedwithout the need for either welding or any other high temperatureoperation.

Other advantages and features of the present invention will becomeapparent to the reader of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exhaust pipe assembly having an exhaust treatmentdevice according to the present invention.

FIG. 2 is a plan view, partly broken-away, of the exhaust treatmentdevice of FIG. 1.

FIG. 3 is an enlarged section of the exhaust treatment device takeninside the circle 3 of FIG. 2.

FIGS. 4-8 illustrate the processing of an exhaust treatment deviceaccording to the present invention.

FIG. 9 illustrates a spin-forming portion of the process illustrated inFIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in FIG. 1, exhaust treatment device is mounted between inletpipe 12 and outlet pipe 14. Inlet pipe 12 is intended to conduct gasesfrom an internal combustion engine to exhaust treatment device 10. Asshown in the various figures, exhaust treatment device 10 has aone-piece, unitary, generally cylindrical housing for containingsubstrate 18. Notice that no welding is required to assemble the presentexhaust treatment device.

Substrate 18 is generally cylindrical in shape and has an outercylindrical surface 18 a (FIGS. 1 and 2) extending between inlet surface18 b and outlet surface 18 c. Although inlet surface 18 b and outletsurface 18 c are shown as being planar, those skilled in the art willappreciate in view of this disclosure that other types of surfaces maybe used in an exhaust treatment device according to the presentinvention. It will be further appreciated in view of this disclosurethat substrate 18 could comprise either a ceramic monolith, or a woundthermal reactor element, or yet other types of exhaust treatment devicesknown to those skilled in the art and suggested by this disclosure. Assuch, the term “substrate”, as used herein, is intended to encompass allof these types of devices.

In the event that substrate 18 is a monolithic ceramic brick, it will benecessary to provide a sealing system which will be applied to thecylindrical outer surface 18 a of substrate 18. As shown in FIGS. 1, 2and 3, a sealing system comprised of wire mesh 22 and metallic V-seals24 is applied to outer surface 18 a. The purpose of wire mesh 22 is tocompressively and securely hold substrate 18 in place within centerportion 16 of the generally cylindrical housing. The purpose of metallicZ-seals 24 is to work in conjunction with the inlet and outlet gasshield and diffusers described below to inhibit the ingress of exhaustgases into the area occupied by wire mesh 22. Those skilled in the artwill appreciate in view of this disclosure that it is possible to useceramic mat material and other types of seals with an exhaust treatmentdevice according to the present invention. Such mat and sealcombinations are well-known to those skilled in the art and several aresuggested by this disclosure.

In order for any exhaust treatment device to function properly, it isnecessary that an inlet diffuser be provided which promotes an evenfield of flow across the entire substrate of the device. Typically,conically shaped diffusers are used. Of course, such conically shapeddiffusers have traditionally been formed by stampingtechniques-techniques which are not suitable for the one-piececonstruction of the exhaust treatment device according to the presentinvention because it is not possible to place stamping tools within theconfines of a device once the substrate has been inserted. Applicantshave solved the problems inherent in making a one-piece exhausttreatment device by using a room temperature or cold-spinning processfor the purpose of forming one-piece integral gas shield and diffusercombinations on either end of the exhaust treatment device.

As shown in FIG. 3, it is essential that the gas shield and diffuserpass, in a tangential position, very closely to the inlet surface 18 b,or, more precisely, the intersection between inlet surface 18 b andcylindrical outer surface 18 a of substrate 18.

As noted above, inlet gas shield and diffuser 26 is produced byspin-forming, which is discussed below in conjunction with FIGS. 6 and7. Because spin-forming cannot produce a straight-sided cone, it isnecessary that a segmented curve be produced for inlet gas shield anddiffuser 26. Various segments of gas shield and diffuser 26 are shown inFIG. 3, beginning with first concave segment 26 a extending betweencenter portion 16 of the housing and a first convex segment 26 b. Notethat convex segment 26 b is tangential to substrate 18 at theintersection of inlet surface 18 b and cylindrical outer surface 18 a ofsubstrate 18. In practice, the inventors of the present device havedetermined that the separation between first convex segment 26 b and theintersection of inlet surface 18 b and cylindrical outer surface 18 a ofsubstrate 18 should be not more than 4 mm for an exhaust treatmentdevice having an outer diameter of approximately 100 mm. It is furthernoted in FIG. 3, that the radius of curvature of first convex section 26b is approximately twice the radius of curvature of first concavesection 26 a. And, the radius of curvature of first concave segment 26 ais about one-tenth of the maximum diameter of the cylindrical housing.Finally, the radius of curvature of first convex segment 26 b isapproximately one-fifth of the maximum diameter of the cylindricalhousing.

The aforementioned geometrical relationships produce an angle, Θ, whichis included between the inner surface of the catalyst housing in thearea of surfaces 26 a and 26 b, of about 45°. In this manner,impingement of exhaust gas upon the sealing system is inhibited, withthe corresponding result that substrate 18 is maintained securely withincenter portion 16 of the cylindrical housing throughout the useful lifeof the present exhaust treatment device.

Inlet gas shield and diffuser 26 is completed by second concave segment26 c and by second convex segment 26 d, which terminates in section 26e, which effectively forms a pipe to which exhaust inlet pipe 12 may beattached.

Segmented outlet gas shield and diffuser 30 is of similar constructionto shield and diffuser 26 and may be spun in the same manner as shieldand diffuser 26. Accordingly, first concave segment 30 a transitionsinto first convex segment 30 b which, in turn, transitions into secondconcave segment 30 c, and thence to second convex segment 30 d. As withinlet gas shield and diffuser 26, final segment 30 e provides aconvenient point for attaching outlet pipe 14.

FIGS. 4-8 illustrate a process according to another aspect of thepresent invention. Prior to entering into a detailed discussion of FIGS.4-8, it should be noted that inlet gas shield and diffuser 26 may bespin-formed prior to swaging of substrate 18 into place within the outerhousing, or spin-forming of inlet gas shield and diffuser 26 may occurafter the swaging operation. What is important is that the spin-formingoperation is capable of producing the very tight tangential fit betweenfirst convex segment 26 b of inlet gas shield and diffuser 26 andsubstrate 18. Other means of forming the exhaust treatment devicehousing, such as pressing or die forming, would simply not lendthemselves to producing devices having the structural configuration of adevice according to the present invention.

FIG. 4 illustrates the first part of a process of producing an exhausttreatment device according to the present invention. FIG. 4 illustratesthe insertion of substrate 18 into center portion 16 of a cylindricalhousing. Locators 32 are used to assure that substrate 16 is locatedprecisely within center portion 16 of the housing.

Turning now to FIG. 5, center portion 16 of the housing is swaged uponsubstrate 18 so that the sealing system, in this case comprising wiremesh 22 and Z-seals 24, is compressed, with the result that substrate 18and the sealing system will be held tightly by center portion 16 so asto avoid breakage of the substrate and/or leakage of gases past thesubstrate, either of which will greatly impair the function of anyexhaust treatment device. The swaging process uses a swaging ram 36which holds the exhaust treatment device within a swaging collet 38,which is described in detail in U.S. Pat. No. 5,724,735, and which isassigned to the assignee of the present invention. Pallet 38 and collar40 cooperate to uniformly reduce the diameter of center section 16 to asmaller value so as to compress the seal system including wire mesh 22and z-seals 24.

Once center portion 16 is swaged down upon the substrate and sealassembly, the process moves to FIG. 6, wherein a first segmented gasshield and diffuser is spun-formed at one end of the tube whichcomprises the housing of the present exhaust treatment device. Thespin-forming is begun by first spin-forming head 50. Then, the oppositeend of the housing is spun by a second spin-forming head 52, as shown inFIG. 7. Finally, the ends of the exhaust treatment device, which arereally the ends of the gas shielding diffusers, are sized, as shown inFIG. 8, by sizers 54, which assures that the openings formed in the gasshields and diffusers are cylindrical so as to accept an exhaust pipe.The spinning process may be performed at room temperature.

FIG. 9 illustrates the central portion 60 of an orbital spin-formingtool of the type known to those skilled in the art and suggested by thisdisclosure. It is noted that central cavity 62 of the central portion 60of the tool has a profile closely approximating the final profile forthe inlet and outlet gas shield and diffuser portions of the present ininvention. Forming cavity 56 engages the cylindrical metallic tube ofthe present device with an orbital or nutational motion as the formingcavity moves axially into engagement with the metallic tube. In thismanner, the inlet and outlet gas shield and diffusers are formed byspinning heads 52.

While the invention has been shown and described in its preferredembodiments, it will be clear to those skilled in the arts to which itpertains that many changes and modifications may be made thereto withoutdeparting from the scope of the invention. For example, the length anddiameter of an exhaust treatment device according to the presentinventive concept may be adjusted to produce a device having a differentaspect ratio, i.e., the ratio of the length to the diameter, by merelychanging the diameter of the tubing and/or the length of the tubingblank from which the device is formed.

What is claimed is:
 1. A flexible manufacturing process for assemblingan exhaust treatment device having opposing ends adapted for attachmentto an inlet pipe and an outlet pipe having a one-piece housing,comprising the steps of: inserting an exhaust treatment substrate into acylindrical metallic tube having a fixed diameter; reducing the diameterof the tube by swaging such that the substrate is held firmly in placewithin the tubing; spin-forming integral gas shielding diffusers fromthe tube at opposite ends of the exhaust treatment device, with each ofsaid gas shielding diffusers comprising first concave segment extendinginwardly at approximately a 45° angle between a center portion of thehousing, and a first convex segment which is tangential to the inletsurface of the substrate, with each of said gas shielding diffusersfurther comprising a second concave segment having a length which isselected to accommodate the diameter of said tube, with said secondconcave segment extending between the first convex segment and a secondconvex segment having a termination to which an exhaust inlet pipe maybe attached.
 2. A process according to claim 1, wherein the gasshielding diffusers are spin-formed at room temperature.
 3. A processaccording to claim 1, further comprising the step of sizing each of thediffusers to allow attachment of the exhaust treatment device to inletand outlet pipes.